Container for temporarily holding water on the roof of a building with a controlled leakage rate

ABSTRACT

According to a first aspect, the invention relates to a container ( 10 ) for temporarily holding water on the roof of a building, including a bottom ( 11 ), a side wall ( 12 ) surrounding the bottom ( 11 ) and an overflow opening ( 14 ) for draining surplus water when the volume of water collected in the container ( 10 ) exceeds a buffer volume, characterised in that the container ( 10 ) includes a water-draining means configured to force water with a temporary storage volume which is lower than the buffer volume to flow according to a regulated leakage rate ( 13 ), and in that the dimensions of the bottom are smaller than the dimensions of a sloping roof on which the container ( 10 ) can be placed so that the water load is distributed evenly on the surface of the roof when a plurality of containers ( 10 ) of the same size cover the surface of the roof.

FIELD OF THE INVENTION

The field of the invention is that of the management of rainwater.

The invention concerns more precisely a device for controlling thedischarge of rainwater on roofs, in particular on sloping roofs.

BACKGROUND OF THE INVENTION

Because of the increasing rain-proofing of urban ground and roofs, themanagement of rainwater is becoming a major problem.

This is because the water cannot infiltrate into rain-proofed ground oron roofs. A major part of the rainwater must therefore be collected andtreated. This collection has a financial cost (pipes, retention basins,water treatment plants), and an ecological cost since the water issoiled by numerous pollutants on its travel (waste, hydrocarbons, heavymetals, etc.).

In addition, a second problem related to the rain-proofing of ground isthe increase risk of flooding. During violent storms, greater andgreater volumes of rainwater run off, giving rise to a saturation ofsewers and overflowing.

Planted roofs afford concrete responses to these two problems since theyoffer a real management of rainwater.

Planted roofs firstly afford management of infiltration.

The planting complex (substrate and plants) in fact captures a majorpart of the annual rain (around 50% according to many tests). The waterstored then returns to the atmosphere by evapotranspiration.

Planted roofs therefore reduce the rain-proofing coefficient of thesurfaces.

In this regard, pre-cultivated containers with no water reserve, such asHydropack® containers from the company Le Prieuré, a description ofwhich will be found in the patent EP 1 044 599 B1, further improve thisfunction. The water reserve contained in the alveoli of such a cell infact increases the retention capacity. The stagnant water will then be“pumped” by the roots of the plants that have developed in thesealveoli.

Planted roofs also allow management of the retention by fulfilling abuffer role (delay effect) during violent storms.

The water accumulates in the planted complex (substrate and plants)until it is saturated with water. Once the complex is saturated, it“salts out” the excess water, like a sponge.

Many tests have proved the advantage of planted roofs in this field. Agood part of the storm waters will therefore be captured by the plantedcomplex. The other part will be “salted out”, once the complex issaturated, a few tens of minutes or even a few hours later. Saturationof sewers is therefore largely attenuated.

Planted roofs thus reduce what is called the run-off coefficient (testshow that this coefficient is 0.4 to 0.6 for a planted roof instead of 1for an impermeable cladding).

The current systems on planted roofs do however have certainlimitations.

Though planted roofs significantly reduce run-off, the coefficient couldbe further reduced.

In addition, though planted roofs reduce the annual mean run-offcoefficient by approximately 50%, they do not provide systematicreduction of each rainy event. This is because the run-off coefficientis not truly mastered but varies substantially according to thecharacteristics of the rainy event and the hydric state of the plantedroof. Thus a planted roof already saturated by previous rain will have arun-off coefficient almost equal to 1 and a zero delay effect, whichresults in a non-reduced leakage rate.

Storing roofs have thus been developed in order to very greatly reduceand control the leakage rate. These storing roofs provide a temporaryretention of the rainwater in order to discharge it at a certain leakagerate.

FIG. 1 shows in this regard a schematic view in section of a possibleexample embodiment of such a storing roof with a zero slope.

The roof 1 has two rain discharge orifices 2, 3.

The first orifice 2 is disposed at the bottom part of the roof 1 so asto afford permanent discharge. The diameter thereof is relatively smallso as to greatly reduce the discharge of water. The diameter is thuscalibrated according to the maximum acceptable leakage rate.

The second orifice 3 fulfils the role of an overflow orifice and has arelatively large diameter. The second orifice 3 is disposed severalcentimetres above the first orifice 2, according to the buffer volumenecessary (as determined statistically by local meteorologicalrecordings, for example, ten-year rain).

Such a storing roof can advantageously also be equipped withpre-cultivated containers with a water reserve, such as the Hydropack®containers presented above. The pre-cultivated containers 4 can for thatpurpose be raised on a honeycomb structure 5 into which the water willinfiltrate.

However, the model of storing roofs cannot at present find applicationexcept for roofs with a zero slope.

This is because, on large roofs, even a small slope (2% or more, as isthe case with industrial, commercial, transport, etc. buildings)represents a significant difference in level. Very high watertight wallswould therefore be necessary to ensure temporary retention of the water.Moreover, the weight distribution would not be even, which would make itnecessary to significantly reinforce the structure of the building atthe slope bottoms.

By way of example, for a building 20 m long, a slope of 3%, represents adifference in level of 60 cm between the top part and the bottom part ofthe roof. In order to store 50 litres of water per m² (on average) onsuch a roof, it is necessary to provide a wall of a minimum of 24.5 cmat the slope bottom. For a building 30 m long and a slope of 3% also, itis necessary to provide a wall 30 cm in height. As for the distributionof weight, the extra load relating to the temporary storage of water atthe slope bottom would be approximately 245 kg/m² in the first case and300 kg/m² in the second case.

Technical constraints (height of roof elevations and extra loads at theslope bottom) thus make it possible to temporarily retain water on roofseven with a low slope.

DISCLOSURE OF THE INVENTION

The objective of the invention is in particular to make it possible totemporarily retain rainwater on roofs having a slope in order to reduceand control the leakage rate thereof.

In this regard, the invention proposes, according to a first aspect, acontainer for temporarily holding water on the roof the building,comprising a bottom, a side wall surrounding the bottom and an overfloworifice for draining surplus water when the volume of water collected bythe device exceeds a buffer volume, characterised in that it compriseswater discharge means configured to force water with a temporary storagevolume that is less than the buffer volume to flow at a regulatedleakage rate, and in that the dimensions at the bottom are smallvis-à-vis dimensions of a sloping roof on which the device can bepositioned so that the water load is distributed evenly on the surfaceof the roof when a plurality of containers with the same size cover thesurface of the roof.

Certain preferred but non-limitative aspects of this container for thetemporary holding of water are as follows:

-   -   the means of discharging water at a regulated leakage rate        comprise an obturator controlled so as to adjust the opening of        a discharge orifice according to the temporary storage volume;    -   the obturator is associated with a float by means of an arm, the        arm being able to pivot in response to the change in the        temporary water storage volume detected by the float in order to        cause a rotation of the obturator in front of or through the        discharge opening;    -   the obturator is a disc portion able to be rotated in front of        the discharge orifice and in which a slope with a progressive        opening is provided, ensuring a constant leakage rate        independent of the height of water in the container;    -   the obturator is a horn able to be rotated through the discharge        orifice, the horn being conformed so as to provide a constant        leakage rate through the discharge orifice, independently of the        height of water in the container;    -   the obturator is a cone able to be driven in translation by a        float through the orifice, the cross-section of the cone        decreasing as the float is approached so that the opening of the        discharge orifice decreases as the water level increases in the        container, thus ensuring a constant leakage rate;    -   the overflow orifice constitutes the discharge orifice;    -   the discharge orifice is distinct from the overflow orifice, the        overflow orifice being arranged above the discharge orifice at a        distance defining the buffer volume;    -   the container also comprises permeable means of supporting a        vegetation complex;    -   the permeable support means are formed a grid supported by one        or more support services defined by little islands extending        from the bottom;    -   the permeable means of supporting the vegetable complex are        formed by a pre-cultivated container conformed so as to fit in        the temporary water holding container, or made in one piece with        the temporary water holding container;    -   the pre-cultivated container has a base in which a plurality of        alveoli are formed, the alveoli being separated by separation        partitions consisting of walls of alveoli extending from the        base and a support surface connecting the top edges of the        walls, a plurality of drainage holes being formed through the        support surfaces;    -   the temporary water holding container comprises a plurality of        separation partitions consisting of walls of alveoli extending        from the bottom and a support surface connecting the top edges        of the walls, forming a plurality of alveoli with the bottom, a        plurality of drainage holes being formed through the support        surfaces in order to form said permeable means of supporting a        vegetation complex;    -   it comprises a permeable bearing slab arranged parallel to the        bottom;    -   it comprises a partial sealed closure extending parallel to the        bottom from the top part of the side wall;    -   the surface area of the bottom is less 2 m², preferably less        than 1 m²;    -   the regulated leakage rate is no more than 10 l/s/ha, and        preferably no more than 5 l/s/ha.

According to another aspect, the invention concerns a system fortemporarily holding water on the roof of a building consisting of aplurality of containers intended to be attached to one another, at leastone of which is a container according to the first aspect of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

Other aspects, aims and advantages of the present invention will emergemore clearly from a reading of the following detailed description ofpreferred embodiments thereof, given by way of non-limited example andmade with reference to accompanying drawings, in which:

FIG. 1, already commented on, is a schematic view section of a storageroof with zero slope;

FIG. 2 shows a possible embodiment of a container according to apossible embodiment of the invention;

FIGS. 3 a-3 b, 5 a-5 b and 6 a-6 b show different possible embodimentsof means of discharging water with a constant leakage rate;

FIG. 7 illustrates a possible embodiment of a container according to aninvention having a residual water storage volume;

FIG. 8 illustrates a possible embodiment of a container according to theinvention having a partial sealed closure;

FIGS. 9 a-9 c illustrate the different possible connections ofcontainers to one another.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 2, this shows a container for the temporary holding ofwater on the roof of a building in accordance with a possible embodimentof the invention.

The container 10 comprises a bottom 11, rectangular in shape in theexample shown, and a side wall 12 surrounding the bottom.

According to the invention, the dimensions of the bottom are smallvis-à-vis the dimensions of a roof, in particular a sloping roof, onwhich the container is intended to be positioned. In this way, the waterload liable to accumulate in the container at the slope bottom issubstantially equivalent to that liable to accumulate in the containerat the top of the slope.

More particularly, the advantage of containers of small size is to beable to distribute the mass of water evenly over the surface of thewhole of the roof. This is because all the containers will routinely andautomatically carry the same mass, at the slope bottom as at the slopetop.

The invention thus proposes to equip a roof by means of a plurality ofsmall temporary water-holding containers, independent of one another.The problem of the distribution of the rainwater (which accumulates atthe slope bottom) and therefore the constraints of excess loads and highwall heights are dispensed with.

The surface area of the solid bottom is for example less than 2 m²,preferably less than 1 m². By way of example, the bottom 11 isrectangular and measures 60 centimetres and 40 centimetres wide.

The container is preferably produced from inert and non-deterioratingmaterial, plastic for example.

The container 10 also comprises an overflow orifice in order todischarge surplus water when the volume of water collected by the deviceexceeds a buffer volume, as well as water discharge means configured toforce water with a temporary storage volume less than the buffer volumeto flow at a regulated leakage rate.

In the context of the invention the leakage rate is preferentially nomore than 10 l/s/ha, even more preferentially no more than 5 l/s/ha. Ingeneral terms, the leakage rate is adapted to the building and thelocation thereof, so as to meet local directives relating to watermanagement. The leakage rate can ideally be reduced to 1 l/s/ha.

According to a first variant shown in FIG. 2, the container 10comprises, at a first height from the bottom 11, discharge means 13configured to allow a discharge of a volume of water less than thebuffer volume at a very low rate and, at a second height from the bottom11, a high-rate overflow orifice 14, the second height being greaterthan the first height so as to define the temporary buffer water storagevolume able to collect storm rain.

These regulated leakage rate discharge means comprise at least one lowrate discharge orifice 13 passing through the side wall at the firstheight, the diameter which is chosen to allow a discharge at low rate,known and controlled. In a variant, these discharge means can be formedby a porous membrane or by a regulator.

The overflow orifice 14 for its part allows high-rate discharge. Thediameter of the overflow orifice is typically greater than that of thelow-rate discharge orifice 13.

The difference in height between the discharge means with a regulatedleakage rate 13 and the overflow discharge means 14 determines a waterstorage buffer volume able to collect storm rain, even of highintensity. The buffer volume will drain away gently after the storm, ata (leakage) rate determined by the rate of the discharge means (forexample by the diameter of the low-rate discharge orifice or orifices13). The buffer volume will once again be empty for a few minutes or afew hours after the storm and will once again be able to completelyfulfil its buffer role during further precipitations.

It should be noted that the first height may be zero (the first waterdischarge means then being arranged in the bottom 11 of the container10). In this case, the container 10 may be raised by legs so that thewater discharge means 13 emerge above any puddles of water present onthe roof.

The first height may also be situated at a few centimetres (by way ofexample, the low-rate discharge orifice 13 is then pierced in the sidewall 12, or in a partition separating alveoli formed in the bottom 11),for example less than 3 centimetres, so as to constitute a smallresidual water storage volume at the bottom of the container (cf. FIG. 5a for example).

It will be noted that, if the discharge means 13 consisted of a simpleorifice, the leakage rate would not be constant. The rate effectivelydecreases as the water height decreases in the container according tothe following mathematical formula: Q=Ω×outlet surface×(2×g×h)^(0.5),where Q designates the leakage rate, Ω is a coefficient relating to thegeometry of the orifice, g designates acceleration due to gravity and hrepresents the water height. By way of example, between water heights of100 mm and 10 mm, the rate could be divided by three.

The invention provides that the opening of a discharge orifice ismodified when the water level decreases or increases, by means of amechanism that adjusts the opening of the orifice according to the waterheight in the container. The means of discharging water at a regulatedleakage rate according to the invention can in particular be configuredso as to close off part of an orifice to a greater or lesser extentaccording to the temporary volume of water so as to discharge water fromthe buffer space according to a constant leakage rate.

In the context of a first variant, the orifice the opening of which isadjusted is a low-rate discharge orifice 13, distinct from the overfloworifice 14, and the surface of which is determined by the buffer volumeand the leakage rate sought.

According to a second variant that will be detailed in more detailhereinafter, the overflow and the temporary water volume are dischargedby one and the same orifice. In this second variant, the orifice theopening of which is adjusted is the overflow orifice itself, the surfaceof which is determined by the overflow rate sought.

Different embodiments of means for discharging water at a constantleakage rate are shown in FIGS. 3 a-3 b, 4 a-4 b, 5 a-5 b and 6 a-6 b.These figures show more particularly the second variant presented abovebut it will be understood that the principles that are shown therein caneasily be used in the context of the first variant, in particularmodifying the form of the obturator.

In each of the variants shown in FIGS. 3 a-3 b, 4 a-4 b and 5 a-5 b, themeans of discharging water at a constant leakage rate comprise a float30 connected to an arm 34 pivoting about a spindle 33 perpendicular tothe wall (FIGS. 3 a-3 b and FIGS. 5 a-5 b) or to the bottom (FIGS. 4 a-4b) of the container and to which an, obturator 32, 37, 38 is connected.The arm 34 pivots in response to the change in height 40 of temporaryholding of water detected by the float 30 and rotates the obturator 32,37, 38 about the spindle 33 in front of or through the orifice 14.

According to a first embodiment shown in FIGS. 3 a and 3 b, theobturator 32 is rotated in front of the orifice 14. The obturator is forexample in the form of a portion of a disc 32 in which a slot 31 withprogressive opening is formed. This progressive opening ensures aconstant leakage rate when the temporary volume of water decreases orincreases by rotating the disc 32 and therefore modifying the positionof the slot in front of the orifice.

In a variant, it is possible to provide, in place a slot formed in adisc portion, a blade the thickness of which varies progressively inorder to ensure a constant leakage rate when the blade closes off theopening.

With reference to FIG. 3 a, the orifice 14 is formed through the wall ofthe container close to the bottom 11 of the container. Theprogressive-opening slot 31 is formed in a disc 32 mounted so as torotate about the rotation spindle 33 perpendicular to the wall. The discis connected to the float 30 via the arm 34 pivoting about the spindle33, so as to pivot against the wall 12 having the orifice in response tochanges in water level in the container as detected by the float. Theopening of the slot 31 widens on approaching the float so that theobturator covers the orifice to a greater extent when a large volume ofwater is to be drained (high pressure) that when a small volume has tobe drained (low pressure). The progressiveness of the opening ensures aconstant leakage rate whatever the volume of water remaining to bedrained.

In order to minimise the risks of clogging, it is also possible to makeprovision for attaching, by adhesive bonding for example, a rod 35 tothe rim of the orifice, the rod being directed towards the inside of thecontainer so as to enter inside the slot 31.

According to a second embodiment shown in FIGS. 4 a-4 b and FIGS. 5 a-5b, the obturator 37, 38 is rotated about a spindle 33 through theorifice 14.

The obturator for example takes the form of a horn 37, 38 associatedwith an arm 34 pivoting about the spindle 33 under the action of a float30 to which it is connected. The horn, the diameter of which increasesprogressively, thus adjusts the opening of the orifice according to thevolume of water remaining to be drained in the container. The orificecan be formed in the bottom of the container (FIGS. 4 a-4 b) or througha wall of the container (FIGS. 5 a-5 b), which creates a residual volumeof water 42.

In the variant shown in FIGS. 6 a-6 b, the means of discharging waterwith a constant leakage rate comprise an obturator 43 directly driven bya float 30 in translation through the orifice 14.

The obturator is for example formed by a cone 43, at the head of which afloat 30 is provided. The orifice 14 is here formed in the bottom of thecontainer, while the cross-section of the cone decreases on approachingthe float. In this way, the opening of the orifice decreases as thewater level increases in the container.

The base of the cone can be sufficiently wide vis-à-vis the surface ofthe orifice in order to hold the obturator in place when the buffervolume (the maximum temporary holding volume) is reached. In this case,the orifice 14 is blocked when the buffer volume is reached and it istherefore necessary to provide a separate overflow orifice in order todischarge the surplus water.

In a variant (cf. FIG. 6 b), it is possible to associate with the baseof the cone a support 46, for example cruciform, carrying vertical lugs47 bearing against the bottom 11 of the container when the buffer volumeis reached, thus holding the obturator in place. In this case, theorifice 14 is completely open when the buffer volume is reached. Thisorifice can therefore also fulfil the role of an overflow orifice.

The reciprocating movement of the obturator can also be guided by meansof a porous pipe 45 that is disposed vertically above the orifice andthe diameter of which exceeds that of the float and obturator, by a fewmillimetres only.

In addition, the float 30 is sized so as to be sufficiently largevis-à-vis the surface of the orifice in order to remain locked insidethe container when the latter is empty, thus holding the obturator.

It will also be noted that the container must be raised by a height atleast equal to the height of the cone.

It should be noted that, in the embodiment shown in FIGS. 4 a-4 b, 5 a-5b and 6 a-6 b, the obturator 37, 38, passes through the orifice. Thecoming and going thus created through the orifice minimises the risks ofclogging. The body of the through obturator can also be provided withroughnesses that facilitate the discharge of particles out of thecontainer.

It was seen previously that, according to a variant embodiment, theoverflow and temporary water volume are discharged through one and thesame orifice. This variant is advantageous in that it makes it possibleto discharge the particles issuing from vegetation complexes associatedwith the temporary water-holding container on a building roof (seebelow). This variant also proves to be advantageous in that it avoidshaving to create upright an overflow orifice, the position of which willvary according to the permissible excess load.

In the context of this variant, the obturator 37, 38, 43 is conformed soas to allow maximum opening of the discharge orifice 14 when then floatreaches its maximum height 41 corresponding to the buffer volume ofwater. The orifice here has a large surface area, for example a diameterof at least 1 cm.

In the context of the embodiment illustrated in FIGS. 3 a and 3 b, theslot 31 formed in the disc is extended by a piercing 36, the surface ofwhich is at least equal to that of the opening 14 so that said piercingcoincides with the orifice when the float 30 reaches its maximum height41.

In the context of the embodiment illustrated, in FIGS. 4 a-4 h and 5a-b, the horn 35 has a recess 39 coming through the orifice when thefloat reaches its maximum height 41.

In the context of the embodiment illustrated in FIGS. 6 a-6 b, a recess44 is hollowed out in the base of the cone, which makes it possible todischarge the overflow through the entire surface of the orifice whenthe base of the cone is upright with respect to the bottom of thecontainer (cf. FIG. 6 b).

It should be noted that, by integrating the low-rate discharge with theoverflow, it is possible to vary the buffer volume according to thepermissible excess load on the roof, while still keeping the samecontainer: the height of the container and the surface area of thedischarge orifice effectively remain the same. This is because, whateverthe obturator in question (disc with slot, horn or cone), it is possibleto adapt the sizing thereof (width of the slot, length of the cone,thickness of the cone or horn, positioning of the overflow recess) tothe required leakage rate and to the permissible maximum excess load.

In the context of a possible embodiment of the invention, a smallresidual water storage space is formed at the bottom of the container,in particular in order to ensure, via synthetic wicks, the supply ofwater to a vegetation complex that will be associated with the temporaryretention container.

To do this, the discharge orifice can be positioned at a certaindistance from the bottom of the container, through a wall (cf. FIGS. 5a-5 b). As shown in FIG. 7, it is also possible to provide one or morepartitions 49 starting from the bottom of the container and extendingover a height less than that of the side wall, the partition orpartitions dividing the container into one or more regions, at least oneof which is not connected to water discharge means and can thus form awater reserve 42.

The stagnant water is then available for the plants in the vegetationcomplex. Synthetic wicks 48 (cf. FIGS. 5 a-5 b and FIG. 7) attached tothe bottom of the container and passing through a vegetation support 49through drainage orifices are connected to a filter 21 (cf. FIG. 5 a) onwhich the vegetation complex rests and conduct the water therebycapillarity.

In addition to control of the leakage rate, the container for temporaryholding of water on the roof of a building according to the inventioncan effectively also allow management of infiltration by providing theuse of a vegetation complex. Some of the rainwater can thus be absorbedby the vegetation complex and then returned to atmosphere byevapotranspiration, which appreciably reduces infiltration.

The rainwater that is not absorbed by the vegetation complex for itspart descends into the container, where the leakage rate of this excesswater will be regulated.

As shown in FIG. 2, the container can for this purpose comprisepermeable means of supporting a vegetation complex 20, where saidvegetation complex is for example formed by a microporous filter 21, alayer of cultivation substrate 22 deposited on the filter 21 andvegetation 23 sown and cultivated on the substrate layer 22.

According to the preferential embodiment of the invention shown in FIG.2, the permeable means of supporting a vegetation complex 20 are formedby a pre-cultivated container, more particularly by a Hydropack®container from the company Le Prieuré (a description of which will befound in the patent EP 1 044 599 B1).

In this FIG. 2, the pre-cultivated container 20 is conformed so as tofit in the temporary water holding container 10.

According to a variant, the pre-cultivated container 20 is made in onepiece with a temporary water holding container 10 so as to form adouble-bottom container. The lower bottom is formed by the bottom 11while the upper bottom is formed by a bottom (base 24 hereinafter)identical to that of the pre-cultivated Hydropack® container.

In these two cases, the pre-cultivated container has a base 24 fromwhich a plurality of alveoli extend.

Each alveolus is closed by a side alveolus wall 25 so as to constitute awater reserve space in which mineral aggregates 26 can be arranged.

The alveoli are preferably connected together by water communicationmeans so that the network of alveoli defines a water reserve, forexample of around 8 litres/m².

The height of the side wall 25 of the alveoli is preferably less thanthe height of the side wall 27 surrounding the base 24 of thepre-cultivated container so that the vegetation complex can be acceptedin the pre-cultivated container 20.

The alveoli are separated by separation partitions consisting ofalveolus side walls 25 extending from the base 24 of the container 20and a support surface 28 connecting the top edges of the alveolus walls25, roughly parallel to the base 24, and on which the vegetation complex21-23 can be arranged.

Drainage holes 29 are pierced in the support surfaces 28 in order toensure permeability of the vegetation complex support means and thusallow rapid discharge of the excess water to the bottom 11 of thetemporary water holding container 10. By way of example, 500 drainageholes 29 per m² are provided, make it possible to sort out the excesswater once the vegetation complex is saturated with water and thealveoli filled with water.

According to another possible embodiment of the invention (not shown),the permeable vegetation complex support means are formed by a gridsupported by one or more support surfaces defined by small islandsextending from the bottom 11 of the temporary water holding container10.

According to yet another embodiment of the invention, the temporarywater holding container 10 itself forms a pre-cultivated container. Thecontainer 10 is for example a Hydropack® container of the type describedpreviously, modified in order to control the leakage rate.

The means of discharging water at a constant leakage rate can thus bearranged at the base 24 of the pre-cultivated container (the base 24here forming the bottom 11 of the temporary holding container) or in thelower part of an alveolus side wall 25.

The height of the alveoli can moreover be modified with respect to thatof a standard Hydropack® container in ardor to increase the waterreserve volume to 50 litres/m² (rather than 8 litres/m). It should benoted that the water reserve no longer exists because of the continuousdischarge: the volume of 50 litres/m² thus corresponds to the buffervolume of the temporary water holding container that will drain out atthe low leakage rate.

The temporary holding container according to the invention is howevernot limited by its use in conjunction with a vegetation complex to allowmanagement of infiltration. The container 10 can thus comprise, insteadof the permeable means of supporting a vegetation complex, a permeablebearing slab arranged parallel to the bottom. The permeable bearing slabis for example a porous slab, in particular a slab made from porouscement.

It will also be noted that, when the temporary water holding containeris disposed on a steep slope, the holding volume is drastically reduced.In an advantageous embodiment of the invention shown in FIG. 8, thecontainer is provided with a partial top sealed closure 50, whichextends for example parallel to the bottom from the upper part of theside wail.

This partial top closure makes it possible to keep a holding volume thatis as great as in the case where the container is disposed on a fiatroof. Moreover, the water issuing from a pre-cultivated containerpositioned above this partial closure, which optionally serves a supportfor it, will pour onto this closure, where it will run off while beingbrought, via the opening 50, into the underlying holding container onthe slope. The pouring of the water from the surface of a container tothe inside of the underlying container is provided by an overflow 52from the partial closure of the first container into the opening 51 ofthe second container (in other words, the water may percolate betweenthe two containers).

In this case, the regulation system will preferentially be arranged atthe edge at the container bottom so that the arm connected to the floatremains perpendicular to the surface of the water.

The container according to the invention advantageously comprises meansof attachment to a similar adjacent container. This facilitates theoperations of placing the containers on roofs, terraces or balconies.

When several containers are thus connected, it is also possibleadvantageously to provide that a single container fulfils the dischargefunction (low-rate and overflow discharge) for a set of containers. Thenumber of discharge systems will thus be reduced.

In addition, by thus connecting the containers, the temporary holdingvolume will be enlarged. It is then possible, for the same leakage ratein question, to enlarge the surface area of the discharge orifice, whichreduces the risks of clogging. On the other hand, if the surface area ofthe discharge orifice is not modified, the leakage rate is reduced.

The containers are connected so as to provide a communication of waterover several square metres.

As shown in FIG. 9 a, the connection 53 can be provided at the containerbottom if it is not wished for there to be any residual water volume.

As discussed previously in relation to FIG. 7, provision can be made forequipping the container fulfilling the discharge function with apartition 49 starting from the bottom defining a residual storage volume42. As shown in FIG. 9 b, the connection 53 between the containers canthen be made at the container bottom. In a variant (cf. FIG. 9 c), theconnection 53 can be arranged at a height determined by the requiredresidual volume.

Finally, it should be noted that the means of discharging water at aconstant leakage rate are not necessarily integrated as such in atemporary water holding container but may form, as is the case in FIGS.9 a-9 c, a separate piece able to be attached to such a container, andin particular to the container at the end of the line when severalcontainers are connected. The use of such an attached piece facilitatesin particular maintenance operations.

REFERENCE SIGNS IN THE DRAWINGS

-   -   1: roof    -   2: leakage rate regulation orifice    -   3: overflow orifice    -   4: pre-cultivated containers    -   5: honeycomb structure    -   10: temporary holding container with controlled leakage rate    -   11: bottom of temporary holding container with controlled        leakage rate    -   12: walls of temporary holding container    -   14: overflow orifice in the bottom or wall the temporary holding        container    -   20: vegetation support    -   1: microporous filter    -   22: cultivation substrate    -   23: vegetation    -   24: base of pre-cultivated container    -   25: side wall of alveoli    -   26: mineral aggregates    -   27: side wall surrounding base 24 of pre-cultivated container 20    -   28: support surface connecting the upper edges of the alveolus        walls    -   29: drainage holes    -   30: float    -   31: slot in the “disc portion” obturator    -   32: “disc portion” obturator    -   33: obturator rotation spindle    -   34: arm connected firstly to the float and secondly to the        obturator    -   35: rod serving to prevent clogging of the orifice    -   36: overflow orifice in “disc portion” obturator    -   37: “horn” obturator passing through the container bottom    -   38: “horn” obturator passing through the container wall    -   39: recess providing the overflow in the horn-shaped obturators    -   40: any water level    -   41: maximum water level, corresponding to maximum permissible        excess load    -   42: residual water volume, serving as reserve plants    -   43: vertical obturator    -   44: recess in vertical obturator    -   45: porous pipe guiding obturator vertically    -   45: cruciform support for vertical obturator    -   47: lugs attached to cruciform support for vertical obturator    -   48: synthetic wick for water to rise to plants by capillarity    -   49: partitions serving to delimit a storage volume    -   50: partial closure of containers to preserve retention capacity        even on a slope    -   51: opening of container by which run-off water enters coming        from container above    -   52: room providing run-off of water from container to container        on a sloping roof    -   53: connection between containers at container    -   54: connection between containers upright with respect to        container bottom

1. Container (10) for temporarily holding water on the roof of abuilding, comprising a bottom (11), a side wall (2) surrounding thebottom and an overflow orifice for draining surplus water when volume ofwater collected by the device exceeds a buffer volume, charactercomprises water discharge means configured to force water with atemporary storage volume that is less than the buffer volume to flow ata regulated leakage rate, and in that the dimensions at the bottom aresmall vis-à-vis dimensions of a sloping roof on which the device can bepositioned so that the water load is distributed evenly on the surfaceof the roof when a plurality of containers with the same size cover thesurface of the roof.
 2. Container according to claim 1, in which themeans of discharging water at a regulated leakage rate comprise anobturator controlled so as to adjust the opening of a discharge orifice(14) according to the temporary storage volume.
 3. Container accordingto claim 2, in which the obturator is associated with a float (30) bymeans of an arm (34), the arm being able to pivot in response to achange in the temporary water storage volume detected by the float inorder to cause a rotation of the obturator in front of or through thedischarge orifice.
 4. Container according to claim 3, in which theobturator is a disc portion (32) able to be rotated in front of thedischarge orifice and in which a slot (31) with a progressive opening isformed, ensuring a constant leakage rate through the slot.
 5. Containeraccording to claim 3, in which the obturator is a horn (37, 38) able tobe driven in rotation through the discharge opening, the horn beingconformed so as to provide a constant leakage rate through the dischargeorifice.
 6. Container according to claim 2, in which the obturator is acone (43) able to be driven in translation by a float (30) through theorifice (14), the cross-section of the cone decreasing on approachingthe float so that the opening of the discharge orifice decreases as thewater level increases in the container, thus ensuring constant leakagerate.
 7. Container according to claim 2, which the overflow orificeconstitutes the discharge orifice.
 8. Container according to claim 2, inwhich the discharge orifice is distinct from the overflow orifice, theoverflow orifice being arranged above the discharge orifice at adistance defining the buffer volume.
 9. Container according to claim 1,further comprising permeable means of supporting a vegetation complex.10. Container according to claim 9, in which the permeable support meansare formed by a grid supported by one or more support surfaces definedby small islands extending from the bottom.
 11. Container according toclaim 9, in which the permeable means of supporting the vegetationcomplex are formed by a pre-cultivated container (20), conformed no asto fit in the temporary water holding container, or made in one piecewith the temporary water holding container.
 12. Container according toclaim 1, in which the pre-cultivated container has a base (24) in whicha plurality of alveoli are for led, the alveoli being separated byseparation partitions consisting of alveolus walls (25) extending fromthe base (24) and a support surface (28) connecting the top edges of thewalls, a plurality of drainage holes (29) being formed through thesupport surfaces.
 13. Container according to claim 9, comprising aplurality of separation partitions consisting of alveolus walls (25)extending front the bottom and a support surface (28) connecting the topedges of the walls, forming a plurality of alveoli with the bottom, aplurality of drainage holes (29) being formed through the supportsurfaces in order to form said permeable means of supporting avegetation complex.
 14. Container according to claim 1, also comprisinga permeable bearing slab arranged parallel to the bottom.
 15. Containeraccording to claim 1, also comprising a partial sealed closure (50)extending from the top part of the side wall.
 16. Container according toclaim 1, the surface area of the bottom of which is less than 2 m²,preferably less than 1 m².
 17. Container according to claim 1, in whichthe regulated leakage rate is no 10 l/s/ha, and preferably no more than5 l/s/ha.
 18. Assembly for the temporary holding of water on the roof ofa building, consisting of plurality of containers attached to oneanother, at least one of which is a container according to claim 1.